Plasma processes occur, for example, in plasma treatment devices and coating devices. Because of the use of a sputtering process and a DC voltage to generate plasma, these devices are also called DC current sputtering systems. In systems of this kind, flashovers often occur, in which a current seeks an electrically conducting passage in the plasma. In particular, flashovers occur during the so-called reactive coating of a substrate. Flashovers can be caused by the circumstance that in addition to the substrate also parts of the sputtering system, such as the inner wall of a process chamber or parts of masks, are coated with electrically non-conducting or poorly conducting materials, which then accumulate charge until a breakdown voltage is reached.
To prevent further damage to the sputtering system, after the occurrence of a flashover, the current supplied by the plasma power supply is switched off, or the current is briefly interrupted. Alternatively, the voltage applied to the plasma chamber can also be short-circuited or reversed in polarity. To initiate the above-cited measures for the suppression of arc discharges, devices for the detection of an arc discharge or arc as well as for the extinction of the arc discharge are necessary for supplying power to the plasma processes and often form an integral part of a plasma power supply.
Detected arc discharges or arcs include those arc discharges that are quickly extinguished without intervention (so-called short arcs) and those that remain in existence for a longer period, and in certain circumstances, can lead to the complete destruction or extinction of the plasma, and to corresponding impairment of the used systems, substrates, etc. (so-called hard arcs).
Because an interruption of the plasma power supply or a reversal in polarity of the same negatively affects the throughput of the plasma process, and because short arcs are self-extinguishing, it is customary not to initiate countermeasures in response to detecting only short arcs.